If cells are grown in media containing amino acids labeled with radioactive nitrogen (¹⁵N), most ofradioactivity will be found in the cells"A) DNA.B) proteins.C) phospholipids.D) DNA and proteins.E) DNA and phospholipids.

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Which of the following elements is NOT correctly matched with its cellular function?A) magnesium and potassium — required as cofactors for enzymesB) sulfur — used for synthesis of thiamin and biotinC) nitrogen — needed for amino acid synthesisD) phosphorus — incorporated into nucleic acidsE) None of the answers is correct; all of the elements are correctly matched.
Pathogenic bacteria isolated from the respiratory or intestinal tracts of humans areA) capnophiles that grow best in carbon dioxide incubators.B) facultative anaerobes that require reducing media for growth. C) strict aerobes that grow best in candle jars.D) capnophiles that prefer highly oxygenated growth conditions. E) strict aerobes that grow best in reducing media.
The biosafety level (BSL) for most introductory microbiology laboratories is A) BSL-1. B) BSL-2. C) BSL-3. D) BSL-4.
The biosafety level for a clinical microbiology laboratory working with potentially airborne pathogens, like tuberculosis bacteria, isA) BSL-1. B) BSL-2. C) BSL-3. D) BSL-4.
A sample of milk is tested for its bacterial content in a plate count assay. A one-milliliter sample ofthe milk is diluted in a 1:10 dilution series. One milliliter of the third dilution tube is plated in apour plate. After incubation, the plate has 54 colonies, indicating that the original milk sample containedA) 54 cells. B) 540 cells. C) 5400 cells. D) 54,000 cells. E) 540,000 cells.
Salts and sugars work to preserve foods by creating A) lower osmotic pressure.B) hypotonic environment. C) lower pH.D) hypertonic environment. E) depletion of nutrients.
The term aerotolerant anaerobe refers to an organism thatA) does not use oxygen but tolerates it.B) uses oxygen or grows without oxygen.C) requires less oxygen than is present in air.D) is killed by oxygen.E) requires more oxygen than is present in air.
Which of the following is an advantage of the standard plate count?A) provides immediate resultsB) determines the number of viable cellsC) can be used to count heat-sensitive bacteriaD) can readily count cells that form aggregatesE) can be performed on very dilute samples, such as lake water
Which of the following is an advantage of the direct microscopic count?A) can easily distinguish live from dead cellsB) requires a large number of cellsC) sample volume is unknownD) requires no incubation timeE) can readily count organisms that are motile
Most bacteria reproduce byA) binary fission. B) fragmentation. C) mitosis. D) aerial hyphae. E) budding.
A culture medium on which only gram-positive organisms grow and a yellow halo surroundsStaphylococcus aureus colonies is called a(n)A) enrichment culture. B) selective medium.C) differential medium.D) selective and differential medium.E) differential and enrichment culture.
A culture medium consisting of agar, peptone, and beef heart is aA) complex medium.B) chemically defined medium.C) selective medium.D) reducing medium.E) differential medium.
Which of the following pairs is mismatched? A) hyperthermophiles — growth at 85°CB) psychrotroph — growth at 0°C C) psychrophile — growth at 15°C D) thermophile — growth at 37°C E) mesophile — growth at 25°C
During which growth phase will gram-positive bacteria be most susceptible to penicillin?A) death phaseB) stationary phaseC) lag phaseD) log phaseE) The culture is equally susceptible during all phases.

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Which of the following is the best definition of generation time?A) the length of time needed for lag phaseB) the duration of log phaseC) the time needed for nuclear divisionD) the length of time needed for a cell to divideE) the minimum rate of doubling
Which of the following is NOT a direct method to measure microbial growth?A) direct microscopic countB) standard plate countC) filtrationD) most probable number (MPN)E) metabolic activity
Which group of microorganisms is most likely to spoil a freshwater trout preserved with salt?A) thermophilesB) anaerobesC) psychrophilesD) hyperthermophilesE) facultative halophiles
Which of the following is an organic growth factor? A) glucoseB) NH₄H₂PO₄C) peptoneD) vitamin B1E) H₂O
Which of the following is an example of a metabolic activity that could be used to measuremicrobial growth?A) MPNB) standard plate countC) glucose consumptionD) turbidityE) direct microscopic count
An experiment began with 4 cells and ended with 128 cells. How many generations did thecells go through?A) 64 B) 32C) 6 D) 5 E) 4
The source of nutrients in nutrient agar isA) agar.B) nutrient.C) peptone and beef extract.D) peptone and NaCl.E) agar and NaCl.